The present invention relates to an exhaust emission purification method and an exhaust emission purification system, in an internal combustion engine mounted on a vehicle, provided with a diesel particulate filter (DPF), in the exhaust gas passage thereof, for which forced regeneration is performed in both of a manual regeneration mode and an automatic regeneration mode.
There is a continuous purification type DPF device as one of exhaust gas purification devices which collect particulate matter (PM) discharged from diesel engines by a filter.
In this continuous purification type DPF device, the PM collected by the DPF is continuously burned and purified and thereby the DPF will self-regenerate, while the exhaust gas temperature is approximately 350° C. or greater. However, when the temperature of exhaust gas, accompanied by low speed/low load or the like is low, the temperature of catalyst drops and the catalyst becomes inactive, so that difficulties arise in oxidizing the PM to enable self-regenerating of the filter. Accordingly, due to the accumulation of PM in the filter, clogging thereof is accelerated in the filter. Therefore, the increase of exhaust gas pressure due to the filter clogging becomes a problem.
Such being the case, when the amount of PM in the filter has exceeded a predetermined amount (threshold), exhaust gas temperature is forcibly raised by means of multi injection (multistage delay injection) or post-injection in a cylinder. Thus, a forced regeneration is performed such that thereby the collected PM is forcibly removed through being burned. By the forced regeneration, hydrocarbon (HC), supplied in the exhaust gas by post-injection or the like, burns at the oxidation catalyst installed on the upstream side of the filter or the oxidation catalyst supported on the filter. With this, the temperature of the exhaust gas is raised at the inlet or on the surface of the filter by utilizing oxidative reaction heat. The exhaust gas raises the temperature of the filter exceeding a temperature at which the PM accumulated on the filter is burned and thus the PM is removed.
The forced regeneration has two modes; i.e., manual regeneration mode and automatic regeneration mode. In the manual regeneration mode, when the clogging on the filter exceeds a predetermined amount, an alarm is issued to a driver. Receiving the alarm, the driver pushes a button for starting the forced regeneration to carry out the forced regeneration. On the other hand, in the automatic regeneration mode, when the clogging on the filter exceeds a predetermined amount, the forced regeneration is carried out without issuing any particular alarm to the driver. In this mode, the forced regeneration is carried out in an automatic mode even when the vehicle is running.
As an example of the manual regeneration, for example, an exhaust gas purification device provided with a forced regeneration means and an operation means (regeneration button) has been proposed (for example, refer to patent document 1). The forced regeneration means forcibly burns particulates collected by a particulate filter (DPF) to remove the same and purify the particulate filter. The operation means is provided on the driver's side to allow a driver to operate the forced regeneration means.
Also, there has been proposed another exhaust gas purification device provided with an indicator lamp (for example, refer to patent document 2). When particulates are accumulated on a particulate filter (DPF) exceeding a threshold at which the purification is required, and at the same time when the temperature of the particulate filter exceeds purification start temperature, the indicator lamp flashes to urge a driver to carry out regeneration of the particulate filter. When the driver operates a regeneration switch, particulates collected on the particulate filter are forcibly burned and removed therefrom. Thus, the particulate filter is regenerated.
With the manual regeneration, a problem that engine oil (lubrication oil) is diluted with unburned fuel, which is supplied by post-injection, and mixed with engine oil (lubrication oil) at the forced regeneration during running; i.e., a problem of oil dilution can be solved. Also, automatic regeneration, which is performed when the problem of oil dilution does not occur, reduces the frequency of the manual regeneration. Therefore, a burden on a driver to input a regeneration control start signal (bring the vehicle to a stop, push of regeneration button or the like) in the case of manual regeneration, can be reduced.
On the other hand, because of various states of operation of the vehicle, there may be cases of urgency regeneration (emergency regeneration). The cases are the case where the DPF is not regenerated satisfactorily even after performing forced regeneration such as manual regeneration or automatic regeneration, and forced regeneration is subsequently carried out; and a case where a large amount of PM is produced from the engine, so that the forced regeneration is carried out so as to cope with the situation.
More specifically, there are the following cases in which the forced regeneration is performed. First case is forced regeneration when judgment is made that the purification is insufficient after ending the purification. Second case is forced regeneration after the time has expired before completing of forced regeneration. And third case is forced regeneration when the pressure difference across the diesel particulate filter exceeds a predetermined judging pressure difference under a state where the traveling distance of vehicle is shorter than a predetermined distance for judgment.
Conventionally, an alarm lamp (DPF LAMP) is provided to issue an alarm in the case of emergency regeneration. The lamp is turned on or flashes to alert a driver to carry out manual regeneration without entering into automatic regeneration. Receiving the alarm, the driver brings the vehicle into a stop and pushes the regeneration button to give a designation to start the manual regeneration. Receiving the designation, a control device performs the manual regeneration.
However, the manual regeneration has a problem such that, upon receiving the alarm, the driver has to carry out steps to bring the vehicle into a stop and then push the manual regeneration button. Therefore, the driver may feel it burdensome. Also, since the manual regeneration is emergency regeneration, there is a problem that, when only the manual regeneration is used, it may cause the following considerable trouble. That is, regardless of the situation that urgently requires carrying out the forced regeneration, when the driver ignores the alarm and does not carry out the manual regeneration, clogging progresses on the DPF.
Patent document 1: Japanese Patent Application Kokai Publication No. 2005-155444
Patent document 2: Japanese Patent Application Kokai Publication No. 2003-155914